1. Field of the Invention
The present invention relates generally to processes for cleaning scrap materials and, more particularly, to a process for cleaning radioactive scrap turnings, such as magnesium thoriated alloy materials, resulting from machining operations in preparation for further processing.
2. Description of the Prior Art
In machining critical components of magnesium for gas turbine engines which must meet close tolerances, it has been found desirable to use a thorium alloy of magnesium. Thorium is a rare earth which, when mixed with the magnesium to the extent of approximately 3%, results in a harder material which provides a superior surface for close tolerance machining.
A drawback of using thorium, however, is the fact that it is a radioactive material, albeit of a low grade nature (LSA-radioactive II) and therefore requires specialized handling, including specialized waste disposal. Thus, after machine operations are performed resulting in scrap turnings, before subsequent operations are performed to recover thoriated magnesium for reuse or to dispose of radioactive fines which cannot be reprocessed because of their small size and which must be properly buried, the turnings and fines must first be cleaned to remove substantially all foreign material. Such foreign material is taken to include ferrous swarf, oil, cutting fluid, and moisture.
The cleaning of cuttings from machining operations to enable recycling of the cuttings is not in itself a new concept. Known apparatus for cleaning newly manufactured articles or scrap materials including turnings and cuttings prior to their reuse has been disclosed in numerous patents. Typical of such patents are U.S. Pat. Nos. 4,719,933 to Jackson, 4,073,301 to Mackinnon, 3,973,573 and 3,754,559, both to Seiwert. A method of cleaning oily metallic cuttings to enable their reprocessing is also disclosed in U.S. Pat. No. 2,852,418 to MacDonald. Additionally, various methods and apparatus for magnetically separating ferrous material from non-ferrous material have long been known and typical disclosures are provided in U.S. Pat. Nos. 3,865,629 to Dankoff et al, 3,198,622 to Herzog et al, 2,954,122 to Colburn, and 2,398,725 to Schutte.
However, in none of these instances has there been any disclosure, or suggestion, of cleaning radioactive materials to enable their further processing, either for purposes of recycling or for purposes of disposal. It was in light of the prior art as just briefly described that the present invention has been conceived and is now reduced to practice.